An electrical junction or outlet box provides an enclosure for an electrical device, such as a receptacle, as well as a termination point for wires carrying electrical current through buildings, houses and other structures. Wiring entering an outlet box is typically connected to a particular electrical fixture or receptacle such as a plug outlet or switch. The box is then typically covered by a face plate having an opening therein to allow access to the outlet or switch while preventing electrified components from being exposed. Outlet boxes may be employed in concealed-wiring installations in which they are located within a wall or ceiling. In such applications, outlet boxes are typically secured to structural members such as wall studs or ceiling joists in order to provide support for the box. The support member must be able to withstand forces imparted onto the box and prevent movement of the box under situations such as the repeated insertion and removal of a plug. Alternatively, outlet boxes may be used in exposed-conduit wiring installations where they are exteriorly mounted to a wall, column or ceiling.
Outlet boxes are available in a variety of configurations and sizes. The selection of a box is dependant upon the specifics of the application. Outlet boxes typically include a plurality of openings which provide entry for the wires into the box. These openings are usually covered by removable portions called “knockouts” which can be easily removed by the installer as required. With most electrical fixtures, the outlet box is spacious enough to accommodate sufficient lengths of excess wiring to allow a connected fixture to be removed from the outlet box and serviced without disconnecting the fixture from the wiring.
The most commonly employed outlet box is a single-gang outlet box, also referred to as a standard outlet box. The single-gang box is ideal for applications in which only one receptacle is required for the application. Standard outlet boxes have opening dimensions of approximately 3″×2¼″ and are available in a variety of depths. Double-gang and triple-gang boxes are also available, and they, typically, have the capacity to hold two and three receptacles, respectively. A four inch (4″) square box is also commonly employed for multiple receptacle applications.
In almost all outlet box designs, electrical devices are attached to the boxes by means of screws. The boxes typically have mounting apertures with female threaded portions located at opposite ends of the box. The electrical device that is to be mounted in the box has a pair of mounting brackets extending on each end of the device with a mounting screw aperture. The device is positioned within the box so that the apertures correspond to the female threaded portions and a mounting screw is inserted through the aperture in the device and into the opening in the corresponding female threaded portion. The screws engage the female threaded portions of the box and are tightened by rotation to secure the device in the box.
To install an electrical fixture such as a receptacle or switch, an installer pulls one end of an electrical wire or cable, through a knockout opening in the box. An excess length of wire is pulled through the knockout allowing for the electrical fixture to be attached to the wire at a location outside the outlet box where the installer has more room to work. The end of the wire is then connected to the terminals of the electrical fixture and the fixture is positioned in the box with the excess wire packed into the box behind the fixture. The installer then holds the fixture in place with one hand while inserting and tightening two mounting screws to secure the fixture to the box.
The methods previously used for installing electrical devices in non-metallic junction boxes with mounting screws fall into two categories—“quick set” and “manual threading.” For the manual threading method, the screws are turned, allowing the threads to dig into the plastic mounting sockets of the box. For the quick set method, the screws are simply pushed into the mounting sockets (usually with a screwdriver or similar tool) and secured in place by various retaining devices. One such device is a metal clip that is inserted inside the socket. The clip has a metal barb that pushes against the threads of the screw with a force opposite to the direction of the insertion. The clip allows the screw to be inserted, but resists extraction of the screw. If the screw begins to loosen or separate, the barb pushes deeper into the thread of the screw and provides an opposing force.
Another retaining device is a separate wedge with internal threads located inside a pocket formed by the screw hole of the junction box. The screw is inserted and the wedge engages the threads of the screw. As the screw is tightened and engages the retaining device, the opposing force created by the wedge increases and pinches the screw threads. However, both of these types of retaining devices have disadvantages. The manual threading devices still require the user to thread the entire screw length and the fast set devices have multiple components which require assembly when manufactured.
Accordingly, it is desirable to provide an electrical outlet box having mounting screw apertures integrally formed with the box which allow the installer to secure the electrical fixture in the box quickly and easily, saving time and money.